Multi-core cable for vehicle

ABSTRACT

A multi-core cable for vehicle includes two power wires, two signal wires, two electric wires, and a sheath. The two power wires have the same size and are made of the same material. The two signal wires have the same size and are made of the same material, and a pair of the two signal wires is twisted and is configured a twisted pair of signal wires. The two electric wires have the same size and are made of the same material, and a pair of the electric wires is twisted and is configured as a twisted pair of electric wires. The two power wires, the twisted pair of signal wires and the twisted pair of electric wires are stranded.

TECHNICAL FIELD

The present invention relates to a multi-core cable for vehicle.

The present application claims priority from Japanese Patent ApplicationNo. 2016-111147 filed on Jun. 2, 2016, the entire content of which isincorporated herein by reference.

RELATED ART

Patent Document 1 discloses a cable in which a cable for feeding powerto an electric parking brake of a vehicle and a cable for connecting awheel speed sensor to an ECU (Electric Control Unit) are integrated.

CITATION LIST Patent Documents

Patent Document 1: JP-A-2014-220043

SUMMARY OF THE INVENTION

A multi-core cable for vehicle in accordance with an aspect of thedisclosure includes:

two power wires each of which includes a first conductor and a firstinsulating layer covering the first conductor,

two signal wires each of which includes a second conductor thinner thanthe first conductor and a second insulating layer covering the secondconductor,

two electric wires each of which includes a third conductor thinner thanthe first conductor and a third insulating layer covering the thirdconductor, and

a sheath covering the two power wires, the two signal wires and the twoelectric wires,

wherein the two power wires have the same size and are made of the samematerial,

wherein the two signal wires have the same size and are made of the samematerial, and a pair of the signal wires is twisted and is configured asa twisted pair of signal wires,

wherein the two electric wires have the same size and are made of thesame material, and a pair of the electric wires is twisted and isconfigured as a twisted pair of electric wires, and

wherein the two power wires, the twisted pair of signal wires and thetwisted pair of electric wires are stranded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view depicting a multi-core cable for vehicle inaccordance with a first embodiment of the present invention.

FIG. 2 is a sectional view depicting a multi-core cable for vehicle inaccordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[Problems to be Solved by Disclosure]

The disclosure is to provide a cable having six or more wires andcapable of being easily secured to a vehicle.

[Effects of Disclosure]

According to the disclosure, a cable having six or more wires andcapable of being easily secured to a vehicle is provided.

<Outline of Embodiments of Present Invention>

First, an outline of embodiments of the present invention is described.

(1) A multi-core cable for vehicle comprises:

two power wires each of which comprises a first conductor and a firstinsulating layer covering the first conductor;

two signal wires each of which comprises a second conductor thinner thanthe first conductor and a second insulating layer covering the secondconductor;

two electric wires each of which comprises a third conductor thinnerthan the first conductor and a third insulating layer covering the thirdconductor; and

a sheath covering the two power wires, the two signal wires and the twoelectric wires,

wherein the two power wires have the same size and are made of the samematerial,

wherein the two signal wires have the same size and are made of the samematerial, and a pair of the signal wires is twisted and is configured asa twisted pair of signal wires,

wherein the two electric wires have the same size and are made of thesame material, and a pair of the electric wires is twisted and isconfigured as a twisted pair of electric wires, and

wherein the two power wires, the twisted pair of signal wires and thetwisted pair of electric wires are stranded.

According to the multi-core cable for vehicle having the aboveconfiguration, it is possible to arrange the two power wires, thetwisted pair of signal wires and the twisted pair of electric wires atone time, so that the arranging man-hour is reduced, as compared to aconfiguration of separately arranging the same. Also, as compared to aconfiguration of separately arranging the two power wires, the twistedpair of signal wires and the twisted pair of electric wires, a spacerequired for the arranging is reduced.

Also, the multi-core cable includes at least the two power wires, onetwisted pair of signal wires and one twisted pair of electric wires. Forthis reason, the wires can be easily disposed in a balanced manner on asection perpendicular to a longitudinal direction of the multi-corecable, and an outer shape of the cable including the sheath is likely tobe close to a circular shape. For this reason, a gap is difficult to beformed at a crimped part of the sheath and a water stop member, so thatthe excellent water stop ability is obtained.

For the above reasons, a cable having six or more wires and capable ofbeing easily secured to a vehicle is provided.

(2) In the multi-core cable for vehicle according to (1), an outerdiameter of the power wire may be 75% to 135% of an outer diameter ofthe twisted pair of signal wires.

According to the multi-core cable for vehicle having the aboveconfiguration, the sizes of the two power wires and the twisted pair ofsignal wires are substantially equal to each other. Therefore, when thewires are stranded, a cable shape including the sheath is close to atrue circle shape, so that the excellent water stop ability is obtained.

(3) In the multi-core cable for vehicle according to (1) or (2), on asection perpendicular to a longitudinal direction of the multi-corecable, centers of the two power wires, a center of the twisted pair ofsignal wires, and a center of the twisted pair of electric wires arepositioned at apexes of a hypothetical quadrangle, and the two powerwires may be provided at diagonal positions.

According to the multi-core cable for vehicle having the aboveconfiguration, a shape obtained by stranding the two power wires, thetwisted pair of signal wires and the twisted pair of electric wires isstable, and a cross-sectional shape of the multi-core cable can beeasily made constant in the longitudinal direction. For this reason,when bending the multi-core cable, the force to be applied to thebending direction of the two power wires, the twisted pair of signalwires and the twisted pair of electric wires is balanced, the load to beapplied to the power wires is reduced, and the power wires are difficultto break.

(4) In the multi-core cable for vehicle according to one of (1) to (3),the first conductor may include a plurality of conductor wires, and

on a section perpendicular to a longitudinal direction of the powerwire, a gap area S3(=S1−S2) obtained by subtracting a total sum S2 ofcross-sectional areas of the conductor wires from an area S1 of a partsurrounded by the first insulating layer may be 5% to 20% of the area S1of the part surrounded by the first insulating layer. Hereinafter, S3/S1is referred to as ‘gap ratio’.

According to the multi-core cable for vehicle having the aboveconfiguration, since the power wire has the gap area of an appropriatemagnitude, it has a drawing force of an appropriate magnitude and theexcellent bending resistance.

(5) In the multi-core cable for vehicle according to one of (1) to (4),the two power wires may be disposed with a gap, and the gap may befilled with fiber.

According to the multi-core cable for vehicle having the aboveconfiguration, it is possible to increase the bending resistance of themulti-core cable.

(6) The multi-core cable for vehicle according to one of (1) to (5), mayfurther comprise:

a second twisted pair of electric wires configured by twisting a pair ofelectric wires having the same size and material, each of the electricwires comprising a fourth conductor thinner than the first conductor anda fourth insulating layer covering the fourth conductor; and

a third twisted pair of electric wires configured by twisting a pair ofelectric wires having the same size and material, each of the electricwires comprising a fifth conductor thinner than the first conductor anda fifth insulating layer covering the fifth conductor,

wherein the two power wires, the twisted pair of signal wires, thetwisted pair of electric wires, the second twisted pair of electricwires and the third twisted pair of electric wires are stranded andcovered with the sheath.

The multi-core cable of the above configuration has the second twistedpair of electric wires and the third twisted pair of electric wires, inaddition to the power wires, the twisted pair of signal wires, and thetwisted pair of electric wires. For this reason, it is possible toarrange the wires at one time and to reduce the arranging man-hour, ascompared to a configuration of separately arranging the same. Also, ascompared to a configuration of separately arranging the wires, a spacerequired for the arranging is reduced.

Also, the wires are disposed in a balanced manner on the sectionperpendicular to the longitudinal direction of the multi-core cable, andan outer shape of the cable including the sheath is likely to be closeto a circular shape. For this reason, a gap is difficult to be formed ata crimped part of the sheath and the water stop member, so that theexcellent water stop ability is obtained.

<Details of Embodiments of Present Invention>

In the below, embodiments of the multi-core cable of the presentinvention will be described in detail with reference to the drawings.

In the meantime, the present invention is not limited to theembodiments, is defined in the claims, and includes all changes madewithin the meaning and scope equivalent to the claims.

First Embodiment

A multi-core cable 1 is used so as to connect an electric control unit(ECU (Electric Control Unit)) mounted on a vehicle and an electricbrake, an electric parking brake, a wheel speed sensor and the likeprovided around a wheel, for example. The wheel is displaceablysupported to a vehicle body via a suspension device and a steeringdevice. In the first embodiment, the multi-core cable 1 is used so as toconnect the ECU fixed to the vehicle body and a component that ismounted to the wheel displaceably supported to the vehicle body.

The multi-core cable 1 is required to be arranged in a small space in atire house in which the wheel is to be accommodated, and to be easilybendable so as not to interfere with displacement of the wheel, and tohave high durability against the bending to be repeatedly appliedthereto.

FIG. 1 is a sectional view depicting the multi-core cable 1 inaccordance with the first embodiment of the present invention. FIG. 1depicts a section perpendicular to a longitudinal direction of themulti-core cable 1. As shown in FIG. 1, the multi-core cable 1 has twopower wires 10, two signal wires 21, two electric wires 31, and a sheath40. In the first embodiment, an outer diameter of the multi-core cable 1may be set to 7 mm to 18 mm, preferably 7.5 mm to 13 mm.

(Power Wire)

The two power wires 10 include, respectively, a first conductor 12, anda first insulating layer 13 configured to cover the first conductor 12.The two power wires 10 have the same size and are made of the samematerial. The power wire is used for transmitting electricity.

The two power wires 10 can be used to connect the electric brake(including an electric parking brake) and the ECU. The electric brakehas a motor configured to drive a brake caliper. For example, one powerwire 10 is used as a power feeding wire configured to feed power to themotor and the other power wire 10 can be used as an earth wire of themotor.

The first conductor 12 is configured by stranding a plurality ofconductors. The conductor is a wire made of copper or copper alloy. Theconductor may be made of a material having predetermined conductivityand flexibility such as copper wire and copper alloy wire. Across-sectional area of the first conductor 12 may be set to 1.5 mm² to3 mm².

The first insulating layer 13 is formed of a flame-retardantpolyolefin-based resin. The first insulating layer 13 may be formed ofcrosslinked flame-retardant polyethylene having a flame retardant mixedthereto. The material of the first insulating layer 13 is not limited tothe flame-retardant polyolefin-based resin (EVA (ethylene-vinyl acetatecopolymer), EEA (ethylene-ethyl acrylate copolymer), EMA(ethylene-methyl acrylate copolymer) and the like), and the othermaterials such as crosslinked fluorine-based resin can also be used. Anouter diameter of the first insulating layer 13 may be set to 2 mm to 4mm.

(Signal Wire)

The two signal wires 21 include, respectively, a second conductor 22thinner than the first conductor 12 and a second insulating layer 23configured to cover the second conductor 22. The two signal wires 21 tobe twisted have the same size and are made of the same material. A pairof the signal wires 21 is twisted and is configured as a twisted pair 20of signal wires. A twisting pitch of the twisted pair 20 of signal wiresmay be set to 10 to 15 times of a twist diameter of the twisted pair 20of signal wires (an outer diameter of the twisted pair 20 of signalwires).

The outer diameter of the twisted pair 20 of signal wires may be set tobe substantially the same as an outer diameter of the power wire 10. Theouter diameter of the power wire 10 is preferably 75% to 135% of theouter diameter of the twisted pair 20 of signal wires. The outerdiameter of the power wire 10 is more preferably 90% to 115% of theouter diameter of the twisted pair 20 of signal wires.

The signal wire 21 can be used to transmit a signal from a sensor or totransmit a control signal from the ECU. The two signal wires 21 can beused for wiring of an ABS (Anti-lock Brake System), for example. The twosignal wires 21 can be respectively used as a wire for connecting adifferential wheel speed sensor and an ECU of a vehicle, for example.

The second conductor 22 may be configured by one conductor, as shown, ormay be configured by stranding a plurality of conductors, like the powerwire 10. The second conductor 22 may be formed of a material, which isthe same as or different from the conductor configuring the firstconductor 12. A cross-sectional area of the second conductor 22 may beset to 0.13 mm² to 0.5 mm².

The second insulating layer 23 may be formed of a material, which is thesame as or different from the first insulating layer 13. An outerdiameter of the second insulating layer 23 may be set to 1.0 mm to 2.2mm.

(Electric Wire)

The two electric wires 31 include, respectively, a third conductor 32thinner than the first conductor 12 and a third insulating layer 33configured to cover the third conductor 32. A pair of the two electricwires 31 is twisted and is configured as a twisted pair 30 of electricwires. The two electric wires 31 to be twisted have the same size andare formed of the same material. The size and material of the electricwire 31 may be the same as those of the signal wire 21. The twisted pair30 of electric wires is preferably twisted in the same direction as thetwisted pair 20 of signal wires. A twisting pitch of the twisted pair 30of electric wires is preferably the same as the twisted pair 20 ofsignal wires. In the meantime, as shown in FIG. 1, when the wires 10,21, 31 are stranded so as to sandwich the two power wires 10 by thesignal wires 21 and the electric wires 31, the force by which therespective wires 10, 21, 31 are stranded are favorably balanced.

An outer diameter of the twisted pair 30 of electric wires may be set tobe substantially the same as the outer diameter of the twisted pair 20of signal wires. The outer diameter of the twisted pair 30 of electricwires may be set to be substantially the same as the outer diameter ofthe power wire 10. The outer diameter of the power wire 10 is preferably75% to 135% of the outer diameter of the twisted pair 30 of electricwires. The outer diameter of the power wire 10 is more preferably 90% to115% of the outer diameter of the twisted pair 30 of electric wires.

The electric wire 31 can be used to transmit a signal from a sensor andto transmit a control signal from the ECU, and can also be used as apower feeding wire for feeding power to an electronic device. Theelectric wire 31 can be used as a power feeding wire, a control wire anda sensor wire, which are to be used for a damper control systemconfigured to change a hydraulic characteristic of the suspension.Alternatively, the electric wire 31 can be used for wiring of anin-vehicle network.

The third conductor 32 may be configured by one conductor, as shown, ormay be configured by stranding a plurality of conductors, like the powerwire 10. The third conductor 32 may be formed of a material, which isthe same as or different from the conductor configuring the firstconductor 12 or the second conductor 22. A cross-sectional area of thethird conductor 32 may be set to 0.13 mm² to 0.5 mm².

The third insulating layer 33 may be formed of a material, which is thesame as or different from the second insulating layer 23. An outerdiameter of the third insulating layer 33 may be set to 1.0 mm to 2.2mm.

(Sheath)

The sheath 40 is configured to cover all the wires including the twopower wires 10, the two signal wires 21 and the two electric wires 31.The two power wires 10, one twisted pair 20 of signal wires and onetwisted pair 30 of electric wires are stranded. The sheath 40 isconfigured to cover the two power wires 10, one twisted pair 20 ofsignal wires and one twisted pair 30 of electric wires stranded.

The sheath 40 includes an inner sheath 41 and an outer sheath 42positioned at an outermore side than the inner sheath 41.

The inner sheath 41 is configured to keep a stranded shape of all thewires including the two power wires 10, the two signal wires 21 and thetwo electric wires 31. The inner sheath 41 is formed by extruding andcoating the same on outer peripheries of the two power wires 10, the twosignal wires 21 and the two electric wires 31. The inner sheath 41 maybe formed of the same material as the outer sheath 42 or a resindifferent from the outer sheath 42. The inner sheath 41 may be formed ofa polyolefin-based resin such as polyethylene and ethylene-vinyl acetatecopolymer (EVA), polyurethane elastomer, polyester elastomer or acomposition formed by mixing at least two thereof. The outer sheath 42or the inner sheath 41 may be formed of crosslinked resin.

The outer sheath 42 is provided so as to protect all the wires includingthe two power wires 10, the two signal wires 21 and the two electricwires 31 from an outside. The outer sheath 42 is formed by extruding andcoating the same on an outer periphery of the inner sheath 41. The outersheath 42 may be formed of crosslinked/non-crosslinked thermoplasticpolyurethane (TPU) having excellent abrasion resistance, for example.Due to the excellent heat resistance, the outer sheath 42 is preferablyformed of crosslinked thermoplastic polyurethane.

An outer diameter of the sheath 40 may be set to 7.5 mm to 11 mm.

(Stranding Direction, Stranding Pitch)

The two power wires 10, the twisted pair 20 of signal wires, and thetwisted pair 30 of electric wires are stranded. A strand diameter of allthe stranded wires may be set to 5.5 mm to 9 mm.

An stranding pitch of all the wires including the two power wires 10,the twisted pair 20 of signal wires and the twisted pair 30 of electricwires may be set to 12 to 24 times of the strand diameter of all thewires including the two power wires 10, the twisted pair 20 of signalwires and the twisted pair 30 of electric wires. When the strandingpitch is less than 12 times of the strand diameter, the multi-core cable1 is likely to break when twisting the same. Also, when the strandingpitch is greater than 24 times of the strand diameter, the power wire 10is likely to break when bending the multi-core cable 1.

In the meantime, a ratio of the stranding pitch of all the wiresincluding the two power wires 10, the twisted pair 20 of signal wiresand the twisted pair 30 of electric wires to the strand diameter of allthe wires is preferably greater than a ratio of the twisting pitch ofthe twisted pair 20 of signal wires to the twist diameter of the twistedpair 20 of signal wires. A stranding direction of all the wires ispreferably opposite to a twisting direction of the twisted pair 20 ofsignal wires and the twisted pair 30 of electric wires.

(Filler)

The multi-core cable 1 may include a filler 50. The filler 50 isprovided inside the sheath 40. The filler 50 may be configured by fibersuch as spun rayon yarn and nylon yarn. The filler 50 may be configuredby tensile strength fiber.

The filler 50 is provided in a gap formed by the two power wires 10. Thefiller 50 may also be provided between the power wire 10 and the signalwire 21, between the power wire 10 and the electric wire 31, between thetwo signal wires 21, and between the two electric wires 31, in additionto the gap between the two power wires 10.

For example, in order to easily form the cross-sectional shape of themulti-core cable 1 to a shape close to a true circle, the filler 50 ispreferably provided inside the sheath 40. Alternatively, in order toincrease the bendability of the multi-core cable 1, the filler 50 may beconfigured by the spun rayon yarn and nylon yarn having a bufferfunction.

(Wrapping Tape)

The multi-core cable 1 may have a wrapping tape 51. The wrapping tape 51is configured to cover the two power wires 10, one twisted pair 20 ofsignal wires and one twisted pair 30 of electric wires. The wrappingtape 51 is configured to stably keep the stranded shape of the wires.The wrapping tape 51 is provided inside the sheath 40.

As the wrapping tape 51, a paper tape, a non-woven fabric tape, a resintape such as polyester and the like can be used. Also, the wrapping tape51 may be spirally wrapped or longitudinally wrapped onto the two powerwires 10, one twisted pair 20 of signal wires and one twisted pair 30 ofelectric wires. Also, a wrapping direction may be a Z wrapping or Swrapping direction. Also, the wrapping direction may be the samedirection as the pair twisting direction of the twisted pair 20 ofsignal wires and the twisted pair 30 of electric wires or may be anopposite direction thereto. The wrapping direction of the wrapping tape51 and the pair twisting direction of the twisted pair 20 of signalwires and the twisted pair 30 of electric wires are preferably oppositeto each other because an unevenness is difficult to occur on a surfaceof the wrapping tape 51 and the outer diameter shape of the multi-corecable 1 can be easily stable.

In the meantime, since the wrapping tape 51 has functions as the filler50 having a buffer function and increasing the bendability and as thesheath 40 having a protection function from an outside, too, when thewrapping tape 51 is provided, it is possible to make the layers of thefiller 50 and the sheath 40 thinner. Like this, when the wrapping tape51 is provided, it is possible to provide the multi-core cable 1 thatcan be more easily bendable and has excellent abrasion resistance.

Also, when providing the sheath 40 of resin by the extrusion coating,the resin enters between the two power wires 10, so that it may bedifficult to separate the two power wires 10 at a terminal of themulti-core cable 1. However, the wrapping tape 51 is provided, so thatit is possible to prevent the resin from entering between the two powerwires 10 and to easily take out the two power wires 10 from theterminal.

(Shield Layer)

The multi-core cable 1 may have a shield layer 52 for suppressing anoise to be emitted outside. The shield layer 52 may be configured bywrapping a metal tape onto the power wires 10, the twisted pair 20 ofsignal wires, the twisted pair 30 of electric wires. The shield layer 52may also be configured by spirally wrapping a plurality of thin metalwires onto the wires. Alternatively, the shield layer 52 may also beconfigured by braiding the thin metal wires. The shield layer 52 may beprovided outside the wrapping tape 51 and inside the sheath 40.

(Effects)

According to the multi-core cable for vehicle 1 of the first embodiment,it is possible to arrange the two power wires 10, the twisted pair 20 ofsignal wires, and the twisted pair 30 of electric wires at one time, andto reduce the arranging man-hour, as compared to a configuration ofseparately arranging the wires. Also, since the two power wires 10, thetwisted pair 20 of signal wires, and the twisted pair 30 of electricwires are integrated as the single multi-core cable 1, a space requiredfor the arranging is reduced, as compared to the configuration ofseparately arranging the two power wires 10, the twisted pair 20 ofsignal wires, the twisted pair 30 of electric wires.

Also, the multi-core cable 1 includes at least the two power wires 10,one twisted pair 20 of signal wires, and one twisted pair 30 of electricwires. For this reason, the corresponding wires are disposed in abalanced manner on the section perpendicular to the longitudinaldirection of the multi-core cable 1, and an outer shape of the cableincluding the sheath 40 is likely to be close to a circular shape. Forthis reason, a gap is difficult to be formed at a crimped part of thesheath 40 and the water stop member, so that the excellent water stopability is obtained. In contrast to the above configuration, when thecross-sectional shape of the sheath 40 is distorted from the true circleor the surface of the sheath 40 has a twisted wave, a gap is formedbetween the sheath 40 and the water stop member, so that the water stopability may be deteriorated.

In the multi-core cable 1 of the above configuration, the outer diameterof the power wire 10 is preferably 75% to 135% of the outer diameter ofthe twisted pair 20 of signal wires. The outer diameter of the powerwire 10 is more preferably 90% to 115% of the outer diameter of thepaired stranded signal wire 20. In the meantime, the outer diameter ofthe power wire 10 means the outer diameter of the first insulating layer13. The outer diameter of the twisted pair 20 of signal wires means adiameter of a hypothetical circumscribed circle on which the pair ofsignal wires 21 is circumscribed, and is two times of the signal wire21.

According to the multi-core cable 1 of the first embodiment, since thesizes of the two power wires 10 and the twisted pair 20 of signal wiressubstantially coincide with each other, it is possible to easilymaintain the twisted shape thereof, and to easily even the diameter ofthe multi-core cable 1 in the longitudinal direction.

Also, since the two power wires 10 and the twisted pair 20 of signalwires are disposed with a predetermined positional relation beingmaintained on the section perpendicular to the longitudinal direction ofthe multi-core cable 1, the cross-sectional shape after the twist isnearly inscribed on the circle. For this reason, it is possible toeasily form the cross-sectional shape of the sheath 40 into asubstantial true circle shape, and a gap is difficult to be formedbetween the sheath 40 and the water stop member, so that the water stopability is further improved.

Also, more preferably, the sizes of the twisted pair 20 of signal wiresand the twisted pair 30 of electric wires substantially coincide witheach other.

As shown in FIG. 1, on the section perpendicular to the longitudinaldirection of the multi-core cable 1, centers C1 of the two power wires10, a center C2 of the twisted pair 20 of signal wires and a center C3of the twisted pair 30 of electric wires are positioned at apexes of ahypothetical quadrangle, and the two power wires 10 are provided atdiagonal positions of the quadrangle.

According to the multi-core cable 1 of the first embodiment, thestranded shape of the two power wires 10, the twisted pair 20 of signalwires and the twisted pair 30 of electric wires is stable, and thecross-sectional shape of the multi-core cable 1 can be easily madeconstant in the longitudinal direction.

Also, when bending the multi-core cable 1 more than once, the load isconcentrated on the thickest wire, so that the thickest wire tends tobreak first. According to the multi-core cable 1 of the firstembodiment, since the power wire 10 is thicker than the signal wire 21and the electric wire 31, the power wire 10 tends to break earlier thanthe signal wire 21 and the electric wire 31. However, according to themulti-core cable 1 of the above configuration, the force that is appliedin the bending direction of the power wires 10, the twisted pair 20 ofsignal wires and the twisted pair 30 of electric wires is balanced, sothat the load to be applied to the thickest power wire 10 is reduced andthe power wire 10 is difficult to break.

In the meantime, the hypothetical quadrangle is preferably a square. Thetwisted shape is more likely to be stable, and the load is difficult tobe concentrated on the power wire 10 when bending the multi-core cable1.

When the first conductor 12 is configured by a plurality of conductorwires, on the section perpendicular to the longitudinal direction of thepower wire 10, a gap area S3(=S1−S2) obtained by subtracting a total sumS2 of cross-sectional areas of the conductor wires from an area S1 of apart surrounded by the first insulating layer 13 is preferably 5% to 20%of the area S1 of the part surrounded by the first insulating layer 13.

When the gap area S3 is less than 5%, the large bending stress islocally applied to the first conductor 12 upon the bending of themulti-core cable 1, so that the bending resistance may be deteriorated.When the gap area S3 is greater than 20%, the power wires 10 moveexcessively freely upon terminal processing of the multi-core cable 1,so that it may be difficult to perform the processing.

In the meantime, the gap area S3 may be obtained by image processing ofbinarizing a shade of a photograph of the section of the multi-corecable 1 into a conductor part and a gap part, specifying a part of theconductor wires of the first conductor 12 from the conductor part, andsubtracting an area of the part of the conductor wires from an area ofthe part surrounded by the first insulating layer 13. For example, animage is made into two levels by software such as “Paint shop pro” (aproduct of Corel Company). A threshold is adjusted with naked eyes sothat a conductor boundary is to be correctly distinguished, and thebinarization is made with a histogram. By specifying the part of theconductor wires of the first conductor 12 with naked eyes, it ispossible to obtain the total sum S2 of the cross-sectional areas of theconductor wires of the first conductor 12, the area S1 of the partsurrounded by the first insulating layer 13, and the gap area S3.

Second Embodiment

FIG. 2 is a sectional view depicting a multi-core cable for vehicle 101in accordance with a second embodiment of the present invention.

In the first embodiment, the multi-core cable 1 having the two powerwires 10, the two signal wires 21 and the two electric wires 31 has beendescribed. However, the present invention is not limited thereto. Forexample, as shown in FIG. 2, a multi-core cable 101 may have fourelectric wires 61, 71, in addition to the two power wires 10, the twosignal wires 21 and the two electric wires 31.

The multi-core cable 101 of the second embodiment includes the two powerwires 10, one twisted pair 20 of signal wires configured by the twosignal wires 21, one twisted pair 30 of electric wires configured by thetwo electric wires 31, one second twisted pair 60 of electric wiresconfigured by the two electric wires 61, and one third twisted pair 70of electric wires configured by the two electric wires 71. The two powerwires 10, one twisted pair 20 of signal wires, one twisted pair 30 ofelectric wires, one second twisted pair 60 of electric wires, and onethird twisted pair 70 of electric wires are stranded and are covered bythe sheath 40.

The second twisted pair 60 of electric wires is configured by a pair ofthe electric wires 61 twisted and configured as a twisted pair ofelectric wires. The two electric wires 61 include, respectively, afourth conductor 62 thinner than the first conductor 12 and a fourthinsulating layer 63 configured to cover the fourth conductor 62. The twoelectric wires 61 have the same size and are made of the same material.

The third twisted pair 70 of electric wires is configured by a pair ofthe electric wires 71 twisted and configured as a twisted pair ofelectric wires. The two electric wires 71 include, respectively, a fifthconductor 72 thinner than the first conductor 12 and a fifth insulatinglayer 73 configured to cover the fifth conductor 72. The two electricwires 71 have the same size and are made of the same material.

The second twisted pair 60 of electric wires and the third twisted pair70 of electric wires may be configured by the same material and size asthe twisted pair 20 of signal wires.

The power wire 10, the twisted pair 20 of signal wires, the twisted pair30 of electric wires are similar to those described in the firstembodiment. The second twisted pair 60 of electric wires and the thirdtwisted pair 70 of electric wires can be used for wiring of anin-vehicle network and wires connected to diverse sensors and devicesand transmitting power and signals.

As shown in FIG. 2, the wrapping tape and the shield layer may not beprovided. When providing the wrapping tape or the shield layer, thepower wires 10, the twisted pair 20 of signal wires, the twisted pair 30of electric wires, the second twisted pair 60 of electric wires, and thethird twisted pair 70 of electric wires are stranded, like themulti-core cable 1 of FIG. 1, and then the wrapping tape or the shieldlayer is provided, and is covered with the sheath 40.

As shown in FIG. 2, on a section perpendicular to a longitudinaldirection of the multi-core cable 101, the two power wires 10 aredisposed with a gap, and the gap is preferably filled with the filler50. Since the thick power wires 10 are not directly in contact with eachother, the power wires 10 are difficult to break even when themulti-core cable is bent more than once.

Also, as shown in FIG. 2, on the section perpendicular to thelongitudinal direction of the multi-core cable 101, the respectivecenters of the power wires 10, the twisted pair 20 of signal wires, thetwisted pair 30 of electric wires, the second twisted pair 60 ofelectric wires, and the third twisted pair 70 of electric wires arepreferably disposed on a circumference of a single circle. On thesection, the power wires 10 are more preferably disposed atpoint-symmetric positions because it is possible to dispose therespective wires 20, 30, 60, 70 in a balanced manner. When the powerwires 10 are disposed to be adjacent to each other, the other wires 20,30, 60 70 do not intersect upon connection of the power wires 10 to themotor, so that it is possible to easily perform the connection.

EXAMPLE

In the below, the multi-core cable for vehicle (Example) of 10 wiresconfigured as shown in Table 1 is described.

The conductor (first conductor) of the power wire was manufactured bystranding seven wires each of which was obtained by stranding 72 copperalloy wires having a diameter of 0.08 mm, and the cross-sectional areaof the conductor was 2.5 mm². The first conductor was covered withcrosslinked flame-retardant polyethylene (first insulating layer) sothat the outer diameter became 3.0 mm. The two power wires are used foran electric parking brake.

The conductor (second conductor) of the twisted pair of signal wires wasmanufactured by stranding three wires each of which was obtained bystranding 16 copper alloy wires having a diameter of 0.08 mm, and thecross-sectional area of the conductor was 0.25 mm². The signal wire wasobtained by covering the second conductor with crosslinkedflame-retardant polyethylene (second insulating layer), and the outerdiameter was 1.4 mm. The twisted pair of signal wires was obtained bytwisting the two signal wires. The twisted pair of signal wires is usedfor ABS.

The third conductor and the fourth conductor had the same configurationas the second conductor. The electric wire including the third conductorand the electric wire including the fourth conductor had the sameconfiguration as the above signal wire, and the twisted pair of electricwires and the second twisted pair of electric wires obtained by twistingthe electric wires had the same configuration as the twisted pair ofsignal wires. The twisted pair of electric wires and the second twistedpair of electric wires are used for in-vehicle network.

The fifth conductor was manufactured by stranding seven wires each ofwhich was obtained by stranding 15 copper alloy wires having a diameterof 0.08 mm, and the cross-sectional area of the conductor was 0.5 mm².The fifth conductor was covered with crosslinked flame-retardantpolyethylene (fifth insulating layer), so that the electric wire havingan outer diameter of 1.7 mm was obtained. The two electric wires weretwisted to obtain the twisted third pair of electric wires. The thirdtwisted pair of electric wires is used for damper control system.

The multi-core cable for vehicle was obtained by wrapping thin paper (awrapping tape made of polyester) onto the two power wires, the twistedpair of signal wires, the twisted pair of electric wires, the secondtwisted pair of electric wires, and the third twisted pair of electricwires, providing the inner sheath (outer diameter: 10.8 mm) made ofcrosslinked polyethylene on an outer side of the thin paper, andcovering an outer side of the inner sheath with the outer sheath (outerdiameter: 12.0 mm) made of crosslinked flame-retardant polyurethane. Themulti-core cable of Example is used to connect the ECU to an electricparking brake, a wheel speed sensor for ABS, an in-vehicle networkdevice, and a device of a damper control system.

Comparative Example

The two power wires for electric parking brake, the twisted pair ofsignal wires for ABS, the twisted pair of electric wires and the secondtwisted pair of electric wires for in-vehicle network, and the thirdtwisted pair of electric wires for damper control system were cabled bycovering the same with the sheath, respectively, without twisting thewires, so that the six cables were obtained. In a cable group ofComparative Example, the power wires were connected to the electricparking brake and the ECU, the twisted pair of signal wires wasconnected to the wheel speed sensor and the ECU, the twisted pair ofelectric wires and the second twisted pair of electric wires wereconnected to the in-vehicle device and the ECU, and the third twistedpair of electric wires was connected to the damper control device andthe ECU.

(Comparison of Example and Comparative Example)

Comparing the cases where the ECU and the diverse devices and the likewere connected using the multi-core cable of Example and the cable groupof Comparative Example, the space required for wiring of the multi-corecable relating to Example is smaller. Also, in the multi-core cable ofExample, since the respective wires are integrated, it is possible toeasily perform the wiring operation.

In particular, in the cable group of Comparative Example, it isnecessary to protect the power wires, the twisted pair of signal wires,and the twisted pair of electric wires, respectively. For this reason,the sheath is required so as to protect the power wires, the twistedpair of signal wires, and the twisted pair of electric wires,respectively. Since the respective wires are covered with the sheath, asummed diameter of the cable group of Comparative Example isconsiderably greater than the diameter of the multi-core cable relatingto Example.

(Repeated Bend Test)

The bending resistance of the multi-core cable was evaluated inaccordance with the repeated bend test prescribed in ISO14572:2011(E)5.9. In the repeated bend test, the multi-core cable wasrepeatedly applied with bending of −90° to +90°. When a reduction amountin resistance value of the power wire from an initial resistance valueafter the bending of 100,000 times was 5% or greater, it was determinedthat the power wire broke. When the reduction amount in resistance valueof the power wire from the initial resistance value was smaller than 5%,the power wire was determined as pass.

In the case of the multi-core cable of Example, the reduction amount inresistance value of the power wire after the bending of 100,000 timeswas smaller than 5%, which means ‘pass’.

(U-Shaped Bend Test)

The evaluation was performed in accordance with an automobile standardJASO C467-977.16 sensor harness bend test set by a public interestincorporated association, Society of Automotive Engineers of Japan, Inc.In the U-shaped bend test, the multi-core table was repeatedly appliedwith the bending from a linear shape to a U shape. After performing thebending 300,000 times at −30°, the bending was continuously performed700,000 times at room temperature. After the test, when there was noexternal abnormality such as breaking and crack and the reduction amountin resistance value of the power wire from the initial resistance valuewas smaller than 5%, the power wire was determined as pass.

In the case of the multi-core cable of Example, even after performingthe bending 300,000 times at −30° and then performing the bending700,000 times at room temperature, there was no external abnormality andthe reduction amount in resistance value was smaller than 5%, whichmeans ‘pass’.

TABLE 1 (10 wires) power wire first conductor material copper alloy wiresize  2.5 SQ (7/72/0.08) first material crosslinked flame- insulatinglayer retardant polyethylene size 3.0 mm twisted pair second materialcopper alloy wire of signal conductor size 0.25 SQ (3/16/0.08) wiressecond material crosslinked flame- insulating layer retardantpolyethylene size 1.4 mm twist number of wires 2 twisted pair thirdmaterial copper alloy wire of electric conductor size 0.25 SQ(3/16/0.08) wires third material crosslinked flame- insulating layerretardant polyethylene size 1.4 mm twist number of wires 2 second fourthmaterial copper alloy wire twisted conductor size 0.25 SQ (3/16/0.08)pair of fourth material crosslinked flame- electric insulating layerretardant polyethylene wires size 1.4 mm twist number of wires 2 thirdfifth material copper alloy wire twisted conductor size  0.5 SQ(7/15/0.08) pair of fifth material crosslinked flame- electricinsulating layer retardant polyethylene wires size  17 mm twist numberof wires 2 bunch number of wires 6 wrapping tape material thin paperinner sheath material crosslinked polyethelene outer diameter 10.8 mm outer sheath material crosslinked flame- retardant polyurethane outerdiameter 12.0 mm 

For the multi-core cables of Examples 2 to 14 of which

1. the gap ratio S3/S1 of the conductor,

2. the ratio of the outer diameter of the power wire to the outerdiameter of the twisted pair of signal wires,

3. the forward or reverse directions of the stranding direction of allthe wires to the twisting direction of the twisted pair of signal wiresand the twisted pair of electric wires, and

4. the ratio of the stranding pitch of the power wires, the twisted pairof signal wires and the twisted pair of electric wires to the strandouter diameter of all the wires were changed with respect to themulti-core cable of six wires of the first embodiment including thepower wires, the twisted pair of signal wires, the twisted pair ofelectric wires, which were the same as the power wires, the twisted pairof signal wires, and the twisted pair of electric wires manufactured inExample, the repeated bend test of 100,000 times, the repeated bend testof 1,000,000 times, the U-shaped bend test and the outer shape wereevaluated. The results are shown in Table 2. In the multi-core cable ofeach example, the centers of the two power wires, the center of thetwisted pair of signal wires, and the center of the twisted pair ofelectric wires were positioned at the apexes of the hypotheticalquadrangle, and the two power wires were provided at the diagonalpositions.

TABLE 2 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7number of wires 6 6 6 6 6 6 power wire 2 2 2 2 2 2 twisted pair ofsignal one pair one pair one pair one pair one pair one pair wirestwisted pair of electric one pair one pair one pair one pair one pairone pair wires 1. gap ratio S3/S1 of  2%  5%  10%  20%  25%  5%conductor 2. ratio of outer 135% 100% 100% 100% 100% 70% diameter ofpower wire to twisted pair of signal wires 3. twisting opposite oppositeopposite opposite opposite opposite direction of twisted pair of signalwires and twisted pair of electric wires and stranding direction of allthe wires 4. stranding pitch to 20 times 12 times 15 times 8 times 20times 20 times strand outer diameter of all the wires repeated bend testpass pass pass pass pass pass (100,000 times) repeated bend test failpass pass pass pass pass (1,000,000 times) U-shaped bend test pass passpass pass pass pass outer shape favorable favorable favorable favorablefavorable The shape is unstable. The roundness is not constant in thelongitudinal direction Example Example Example Example Example ExampleExample 8 9 10 11 12 13 14 number of wires 6 6 6 6 6 6 6 power wire 2 22 2 2 2 2 twisted pair of signal one pair one pair one pair one pair onepair one pair one pair wires twisted pair of electric one pair one pairone pair one pair one pair one pair one pair wires 1. gap ratio S3/S1 of 5%  5%  5%  5%  5%  5%  5% conductor 2. ratio of outer diameter 75% 90%115% 135% 140% 135% 135% of power wire to twisted pair of signal wires3. twisting direction opposite opposite opposite opposite opposite thesame opposite of twisted pair of signal wires and twisted pair ofelectric wires and stranding direction of all the wires 4. strandingpitch to 12 times 12 times 12 times 12 times 15 times 15 times 25 timesstrand outer diameter of all the wires repeated bend test pass pass passpass pass pass pass (100,000 times) repeated bend test pass pass passpass fail pass fail (1,000,000 times) U-shaped bend test pass pass passpass pass pass pass outer shape favorable favorable favorable favorableThe shape The shape favorable is is unstable. unstable. The Theroundness roundness is not is not constant constant in the in thelongitudinal longitudinal direction. direction.

As shown in Table 2, for all Examples, the results of the repeated bendtest and the U-shaped bend test of 100,000 times were pass.

In the case of Example 2 for which the result of the repeated bend testof 1,000,000 times was fail, it is thought that the reason for this isthat the gap ratio S3/S1 of the conductor is too small.

In the case of Example 12 for which the result of the repeated bend testof 1,000,000 times was fail, it is thought that the reason for this isthat the power wire is too thick with respect to the twisted pair ofsignal wires or the twisted pair of electric wires.

In the case of Example 14 for which the result of the repeated bend testof 1,000,000 times was fail, it is thought that the reason for this isthat the stranding pitch of the power wire, the twisted pair of signalwires and the twisted pair of electric wires is too large with respectto the strand outer diameter of all the wires.

In the case of Example 7 of which the roundness is not constant in thelongitudinal direction, it is thought that the reason for this is thatthe power wire is too thin with respect to the twisted pair of signalwires or the twisted pair of electric wires.

In the case of Example 12 of which the roundness is not constant in thelongitudinal direction, it is thought that the reason for this is thatthe power wire is too thick with respect to the twisted pair of signalwires or the twisted pair of electric wires.

In the case of Example 13 of which the roundness is not constant in thelongitudinal direction, it is thought that the reason for this is thatthe twisting direction of the twisted pair of signal wires and thetwisted pair of electric wires and the stranding direction of all thewires are the same.

In the meantime, in the case of the multi-core cables of Examples 2 to14, even after the cables were bent 1,000,000 times, it was not observedthat the wires such as the signal wires, except for the power wires,broke.

DESCRIPTION OF REFERENCE NUMERALS

1, 101: multi-core cable

10: power wire

12: first conductor

13: first insulating layer

20: twisted pair of signal wires

21: signal wire

22: second conductor

23: second insulating layer

30: twisted pair of electric wires

31: electric wire

32: third conductor

33: third insulating layer

40: sheath

41: inner sheath

42: outer sheath

50: filler

51: wrapping tape

52: shield layer

60: second twisted pair of electric wires

61: electric wire

62: fourth conductor

63: fourth insulating layer

70: third twisted pair of electric wires

71: electric wire

72: fifth conductor

73: fifth insulating layer

The invention claimed is:
 1. A multi-core cable for vehicle comprising:two power wires each of which comprises a first conductor and a firstinsulating layer covering the first conductor; two signal wires each ofwhich comprises a second conductor thinner than the first conductor anda second insulating layer covering the second conductor; two electricwires each of which comprises a third conductor thinner than the firstconductor and a third insulating layer covering the third conductor; anda sheath covering the two power wires, the two signal wires and the twoelectric wires, wherein the two power wires have a same size and aremade of a same material, wherein the two signal wires have a same sizeand are made of a same material, and a pair of the signal wires istwisted and is configured as a twisted pair of signal wires, wherein thetwo electric wires have a same size and are made of a same material, anda pair of the electric wires is twisted and is configured as a twistedpair of electric wires, wherein the two power wires, the twisted pair ofsignal wires and the twisted pair of electric wires are stranded,wherein the two power wires are disposed with a gap therebetween, andthe gap is filled with fiber, and wherein the twisted pair of electricwires is twisted in a same direction as the twisted pair of signalwires.
 2. The multi-core cable for vehicle according to claim 1, whereinan outer diameter of each power wire is 75% to 135% of an outer diameterof each twisted pair of signal wires.
 3. The multi-core cable forvehicle according to claim 1, wherein on a section perpendicular to alongitudinal direction of the multi-core cable, centers of the two powerwires, a center of the twisted pair of signal wires, and a center of thetwisted pair of electric wires are positioned at apexes of ahypothetical quadrangle, and the two power wires are provided atdiagonal positions.
 4. The multi-core cable for vehicle according toclaim 1, wherein the first conductor includes a plurality of conductorwires, and wherein on a section perpendicular to a longitudinaldirection of the power wire, a gap area S3(=S1−S2) obtained bysubtracting a total sum S2 of cross-sectional areas of the conductorwires from an area S1 of a part surrounded by the first insulating layeris 5% to 20% of the area S1 of the part surrounded by the firstinsulating layer.
 5. The multi-core cable for vehicle according to claim1, further comprising: a second twisted pair of electric wiresconfigured by twisting a pair of electric wires having a same size andmaterial, each of the electric wires comprising a fourth conductorthinner than the first conductor and a fourth insulating layer coveringthe fourth conductor; and a third twisted pair of electric wiresconfigured by twisting a pair of electric wires having a same size andmaterial, each of the electric wires comprising a fifth conductorthinner than the first conductor and a fifth insulating layer coveringthe fifth conductor, wherein the two power wires, the twisted pair ofsignal wires, the twisted pair of electric wires, the second twistedpair of electric wires and the third twisted pair of electric wires arestranded and covered with the sheath.
 6. The multi-core cable forvehicle according to claim 1, further comprising: a wrapping tapeconfigured to cover the two power wires, the two signal wires and thetwo electric wires, wherein the wrapping tape is a paper tape, anon-woven fabric tape, or a resin tape.
 7. The multi-core cable forvehicle according to claim 1, wherein a twisting pitch of the twistedpair of signal wires is set to 10 to 15 times of a twist diameter of thetwisted pair of signal wires.
 8. The multi-core cable for vehicleaccording to claim 1, wherein a twisting pitch of the twisted pair ofelectric wires is the same as a twisting pitch of the twisted pair ofsignal wires.
 9. The multi-core cable for vehicle according to claim 1,wherein a stranding pitch of all the two power wires, the twisted pairof signal wires, and the twisted pair of electric wires is set to 12 to24 times of a strand diameter of all the two power wires, the twistedpair of signal wires, and the twisted pair of electric wires.
 10. Themulti-core cable for vehicle according to claim 1, wherein the wrappingtape is spirally wrapped on the two power wires, the two signal wires,and the two electric wires.
 11. The multi-core cable for vehicleaccording to claim 1, wherein a wrapping direction of the wrapping tapeis opposite to a twisting direction of the twisted pair of signal wiresand the twisted pair of electric wires.